Using LocalDB on Microsoft SQL Server

Overview

Microsoft SQL Server 2016 Express LocalDB is a feature of SQL Server Express targeted to developers. It is available on SQL Server 2016 Express with Advanced Services.

LocalDB installation copies a minimal set of files necessary to start the SQL Server Database Engine. Once LocalDB is installed, you can initiate a connection using a special connection string. When connecting, the necessary SQL Server infrastructure is automatically created and started, enabling the application to use the database without complex configuration tasks. Developer Tools can provide developers with a SQL Server Database Engine that lets them write and test Transact-SQL code without having to manage a full server instance of SQL Server.

Install LocalDB

Install LocalDB through the installation wizard or by using the SqlLocalDB.msi program. LocalDB is an option when installing SQL Server 2016 Express.

Select LocalDB on the Feature Selection/Shared Features page during installation. There can be only one installation of the LocalDB binary files for each major SQL Server Database Engine version. Multiple Database Engine processes can be started and will all use the same binaries. An instance of the SQL Server Database Engine started as the LocalDB has the same limitations as SQL Server Express

An instance of SQL Server Express LocalDB is managed by using the SqlLocalDB.exe utility. SQL Server Express LocalDB should be used in place of the SQL Server Express user instance feature which is deprecated.

Description

The LocalDB setup program uses the SqlLocalDB.msi program to install the necessary files on the computer. Once installed, LocalDB is an instance of SQL Server Express that can create and open SQL Server databases. The system database files for the database are stored in the users' local AppData path which is normally hidden. For example C:\Users\\AppData\Local\Microsoft\Microsoft SQL Server Local DB\Instances\LocalDBApp1\. User database files are stored where the user designates, typically somewhere in the C:\Users\\Documents\ folder.

For more information about including LocalDB in an application, see the Visual Studio documentation Local Data Overview, Walkthrough: Creating a SQL Server LocalDB Database, and Walkthrough: Connecting to Data in a SQL Server LocalDB Database (Windows Forms).

For more information about the LocalDB API, see SQL Server Express LocalDB Instance API Reference and LocalDBStartInstance Function.

The SqlLocalDb utility can create new instances of LocalDB, start and stop an instance of LocalDB, and includes options to help you manage LocalDB. For more information about the SqlLocalDb utility, see SqlLocalDB Utility.

The instance collation for LocalDB is set to SQL_Latin1_General_CP1_CI_AS and cannot be changed. Database-level, column-level, and expression-level collations are supported normally. Contained databases follow the metadata and tempdb collations rules defined by Contained Database Collations.

Restrictions

LocalDB cannot be a merge replication subscriber.

LocalDB does not support FILESTREAM.

LocalDB only allows local queues for Service Broker. An instance of LocalDB owned by the built-in accounts such as NT AUTHORITY\SYSTEM can have manageability issues due to windows file system redirection; Instead use a normal windows account as the owner.

Automatic and Named Instances

LocalDB supports two kinds of instances: Automatic instances and named instances.

  • Automatic instances of LocalDB are public. They are created and managed automatically for the user and can be used by any application. One automatic instance of LocalDB exists for every version of LocalDB installed on the user’s computer. Automatic instances of LocalDB provide seamless instance management. There is no need to create the instance; it just works. This allows for easy application installation and migration to a different computer. If the target machine has the specified version of LocalDB installed, the automatic instance of LocalDB for that version is available on the target machine as well. Automatic instances of LocalDB have a special pattern for the instance name that belongs to a reserved namespace. This prevents name conflicts with named instances of LocalDB. The name for the automatic instance is MSSQLLocalDB.
  • Named instances of LocalDB are private. They are owned by a single application that is responsible for creating and managing the instance. Named instances provide isolation from other instances and can improve performance by reducing resource contention with other database users. Named instances must be created explicitly by the user through the LocalDB management API or implicitly via the app.config file for a managed application (although managed application may also use the API, if desired). Each named instance of LocalDB has an associated LocalDB version that points to the respective set of LocalDB binaries. The instance name of a LocalDB is sysname data type and can have up to 128 characters. (This differs from regular named instances of SQL Server, which limits names to regular NetBIOS names of 16 ASCII chars.) The name of an instance of LocalDB can contain any Unicode characters that are legal within a filename. A named instance that uses an automatic instance name becomes an automatic instance.

Different users of a computer can have instances with the same name. Each instance is a different processes running as a different user.

Shared Instances of LocalDB

To support scenarios where multiple users of the computer need to connect to a single instance of LocalDB, LocalDB supports instance sharing. An instance owner can choose to allow the other users on the computer to connect to his instance. Both automatic and named instances of LocalDB can be shared. To share an instance of LocalDB a user selects a shared name (alias) for it. Because the shared name is visible to all users of the computer, this shared name must be unique on the computer. The shared name for an instance of LocalDB has the same format as the named instance of LocalDB.

Only an administrator on the computer can create a shared instance of LocalDB. A shared instance of LocalDB can be unshared by an administrator or by the owner of the shared instance of LocalDB. To share and unshared an instance of LocalDB, use the LocalDBShareInstance and LocalDBUnShareInstance methods of the LocalDB API, or the share and unshared options of the SqlLocalDb utility.Only an administrator on the computer can create a shared instance of LocalDB. A shared instance of LocalDB can be unshared by an administrator or by the owner of the shared instance of LocalDB. To share and unshared an instance of LocalDB, use the LocalDBShareInstance and LocalDBUnShareInstance methods of the LocalDB API, or the share and unshared options of the SqlLocalDb utility.

Starting LocalDB and Connecting to LocalDB

Connecting to the Automatic Instance

The easiest way to use LocalDB is to connect to the automatic instance owned by the current user by using the connection string "Server=(localdb)\MSSQLLocalDB;Integrated Security=true". To connect to a specific database by using the file name, connect using a connection string similar to "Server=(LocalDB)\MSSQLLocalDB; Integrated Security=true ;AttachDbFileName=D:\Data\MyDB1.mdf".

Creating and Connecting to a Named Instances

In addition to the automatic instance, LocalDB also supports named instances. Use the SqlLocalDB.exe program to create, start, and stop an named instance of LocalDB. For more information about SqlLocalDB.exe, see SqlLocalDB Utility.

    REM Create an instance of LocalDB  
    "C:\Program Files\Microsoft SQL Server\130\Tools\Binn\SqlLocalDB.exe" create LocalDBApp1  
    REM Start the instance of LocalDB  
    "C:\Program Files\Microsoft SQL Server\130\Tools\Binn\SqlLocalDB.exe" start LocalDBApp1  
    REM Gather information about the instance of LocalDB  
    "C:\Program Files\Microsoft SQL Server\130\Tools\Binn\SqlLocalDB.exe" info LocalDBApp1

The last line above, returns information similar to the following.

    Name	"LocalDBApp1"
    Version	<Current Version>
    Shared name	""
    Owner	"<Your Windows User>"
    Auto create	No
    State	running
    Last start time	<Date and Time>
    Instance pipe name	np:\\.\pipe\LOCALDB#F365A78E\tsql\query

Connecting to a Shared Instance of LocalDB

To connect to a shared instance of LocalDB add .\ (dot + backslash) to the connection string to reference the namespace reserved for shared instances. For example, to connect to a shared instance of LocalDB named AppData use a connection string such as (localdb)\.\AppData as part of the connection string. A user connecting to a shared instance of LocalDB that they do not own must have a Windows Authentication or SQL Server Authentication login.

Troubleshooting

For information about troubleshooting LocalDB, see Troubleshooting SQL Server 2012 Express LocalDB

Permissions

An instance of SQL Server 2016 ExpressLocalDB is an instance created by a user for their use. Any user on the computer can create a database using an instance of LocalDB, storing files under their user profile and running the process under their credentials. By default, access to the instance of LocalDB is limited to its owner. The data contained in the LocalDB is protected by file system access to the database files. If user database files are stored in a shared location, the database can be opened by anyone with file system access to that location by using an instance of LocalDB that they own. If the database files are in a protected location, such as the users data folder, only that user, and any administrators with access to that folder, can open the database. The LocalDB files can only be opened by one instance of LocalDB at a time.